Design and Implementation of On-board Electrical Power ... - OUFTI-1

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Chapter 2Requirements of the EPS2.1 IntroductionThe first step before beginning the design of the EPS is to know exactly what our goals andour constraints are. This is the subject of this chapter.There are constraints due to space environment. The EPS must withstand vacuum andwide ranges of temperatures and radiations. There are constraints linked to the launch, likeaccelerations, vibrations, and rules for the CubeSats in the Vega launch vehicle. Finally, thereare constraints due to the construction of OUFTI-1. The dimensions of the electronic cardsand available volumes are specified.The desired functionalities also guide the design. The EPS must produce enough energyto supply the CubeSat. Enough energy has to be stored to supply the satellite during theperiod of eclipse. The EPS must provide several power outputs with stabilized voltages.The constraints will also guide the validation tests applied to the prototypes. Most ofelectrical and temperature tests were done on the engineering model this year. Batteries weretested under vacuum. Complete vibration tests and maybe radiation tests will be carried outnext year.Most functionalities and constraints were known as soon as the project started. Butthere were also functionalities and constraints that came from an iterative work. From thefirst requirements, design choices were made. These choices brought new constraints anda new iteration began. At each development step, interaction with other teams also had ahuge influence on the design and requirements. Reporting here all iterations and each newdevelopment would lead to write a long document. As a consequence, this report is most oftime focused on the last iteration in the development process.12
2.2 Constraints2.2.1 Space EnvironmentVacuumThe satellite is expected to be released in an elliptical orbit with an altitude between 350 and1,200km [4]. At such altitudes, the atmosphere pressure can be neglected and considered asvacuum. Therefore, all components used in the satellite must withstand vacuum. The twothreats of vacuum are:• Deformations due to mechanical constraint of vacuum• Out gassing.The most sensitive component of the EPS is the batteries.RadiationsCharged particles of solar wind, electrons, and protons, are captured by the earth magneticfield. They form the radiations belts, also known as the Van-Allen belts. There are two belts:• The inner belt, between 1,000 and 15,000 km, containing high concentrations of energeticprotons with energies exceeding 100 MeV and electrons in the range of hundreds of keV.• The outer belt, extending till 50,000km, and consisting mainly of high energy electrons(from 0.1 to 10 MeV).Figure 2.1: Van Allen Belts.The apogee of OUFTI-1 is in the inner belt.Spacecrafts need to be protected against radiations, especially if they go though the radiationbelts. Trapped particles in the radiation belts and cosmic rays can cause “Single EventPhenomena” (SEP) within semiconductor devices. There are three different types of SEP:13
Page 2 and 3: AcknowledgementsI want to thank the
Page 4 and 5: Contents1 Introduction 91.1 Cubesat
Page 6 and 7: 4.4.2 Mean case . . . . . . . . . .
Page 8 and 9: B Power budget worksheet 106C Pictu
Page 10 and 11: design and the tests are delegated
Page 14 and 15: • The Single-Event Upset (SEU)Thi
Page 16 and 17: the P-POD. RBF pins must fit within
Page 18 and 19: Figure 2.6: Top view of the PC104 c
Page 20 and 21: Chapter 3Design of EPS architecture
Page 22 and 23: • Voltage (4) and current (5) at
Page 24 and 25: Figure 3.6: The equivalent circuit
Page 26 and 27: of our Lithium-Polymer batteries va
Page 28 and 29: Figure 3.12: I-V curve of a solar p
Page 30 and 31: 3.3.3 CapacityA important value to
Page 32 and 33: Parameter SLPB723870H4 SLPB554374HN
Page 34 and 35: of the batteries is kept between -2
Page 36 and 37: Over Charge Prohibition 4.275 ± 0.
Page 38 and 39: supplied in 5V. The circuit will be
Page 40 and 41: Chapter 4The Power Budget4.1 Introd
Page 42 and 43: Figure 4.1: P-V curve of a solar pa
Page 44 and 45: 4.3.2 Efficiency of convertersTo at
Page 46 and 47: Figure 4.3: Consumptions in % in me
Page 48 and 49: Chapter 5Electrical Design of EPS5.
Page 50 and 51: V outV in= D. (5.1)Since D ≤ 1, t
Page 52 and 53: The power losses in the inductor ar
Page 54 and 55: ∆i L,1 + ∆i L,2 = 0, (5.16)V in
Page 56 and 57: Using the value of ∆i L given by
Page 58 and 59: There is no data about the case to
Page 60 and 61: Capacitor selectionFour 10µF ceram
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• Output voltage: 5V.• Maximum
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Figure 5.12: Burst mode operation (
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Figure 5.14: Simplified schematics
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Figure 5.15: Worksheet for 3.3V con
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sequently, the k was chosen above 0
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where G 1 is the initial control-to
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Figure 5.21: Measured Bode diagram
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Figure 5.26: Equivalence between th
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C f =12πf f R 0f,L f = R 2 0f C f
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Figure 5.37: Schematics of the firs
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R KR >1.45V100mA − 1.3A35= 23.07
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The schematics is shown on figure 5
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A commercial model meets all requir
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Figure 5.45: Schematics of the heat
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PrefixX7X5Y5Z5SuffixTemperature ran
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6.2.1 The second dissipation system
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• The antenna deployment system.
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6.3.3 TestsThe engineering model of
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7.3 ActivitiesAs OUFTI-1 is designe
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8.1.2 DesignA model of Li-Po batter
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[15] Fabien Jordan, Phase B Electri
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TaK = 273 + TaC;%Photo-current ther
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Appendix BPower budget worksheetIn
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108
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Appendix CPictures of the prototype
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Appendix DSchematics of the enginee
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876543213V3 CONVERTER AND INPUT FIL
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87654321ANTENNA DEPLOYMENT CIRCUITB
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